I want to ask is there an articulation that is opposite from 'Fermata'. In other words I don't want to change the time signature? What I want the particular note/silence should go faster then the running tempo. I'm transcribing old A Capella melodies from cassettes, where the tempo in general isn't rigid to the beat, it flows slower or faster. The differences could be even in a single measure and even a single note. Thank you all for the combined knowledge it adds to everyone.
The answer to the question needn't involve creating a new type of articulation.
Perhaps the tempo change actually occurs earlier, and your bar 100 should look more like your bar 105, using 16th notes rather than triplet 8th notes?
Or instead, if you look at bar 99, are you certain that the rest at the end of the bar is precisely a quarter note? Perhaps you could re-notate bar 100 so that it still uses triplet 8th notes but has a rest at the start of the bar. That way you won't need a eighth note rest at the end of the bar, so you wouldn't then need the new articulation on that eighth note rest indicating to actually play it shorter than an eighth note.